As semiconductor devices are miniaturized in size, the demand for reducing a parasitic capacitance between a gate and a source of a transistor is increasing. For this reason, a film (e.g., a low-k film) having a relatively lower dielectric constant is considered in manufacturing semiconductor devices, instead of a silicon nitride film (i.e., SixNy film, hereinafter, simply referred to as “SiN film”), which is conventionally used as a sidewall film or the like. In a silicon oxycarbonitride film (SiOCN film) in which oxygen (O) and carbon (C) are added to the SiN film, a low dielectric constant is realized by adding O, and a wet etching resistance or a dry etching resistance which is deteriorated by adding O can be recovered or improved by adding C.
It is known that the SiOCN film, which is a thin film containing a predetermined element such as silicon, oxygen, carbon and nitrogen, is formed, for example, by performing a cycle a predetermined number of times, the cycle including: supplying a silicon-containing gas to a heated wafer in a process chamber; supplying a carbon-containing gas; supplying a nitriding gas; and supplying an oxidizing gas.
Recently, since a high dielectric constant insulating film (high-k film) is used as a gate insulating film of transistors, it is increasingly required that a film forming temperature of a thin film formed near a gate, such as a sidewall film, is lowered to a low temperature range, for example, of 600 degrees C. or less, or 450 degrees C. or less. However, when the film forming temperature is lowered to such a low temperature range, a film forming rate of a thin film is reduced, causing a low productivity of semiconductor devices.
Also, if the film forming temperature of the SiOCN film is lowered, in some cases, an oxygen (O) concentration and a carbon (C) concentration are respectively reduced and a nitrogen (N) concentration is increased as the film forming temperature is lowered. That is, in some cases, a composition of the SiOCN film approaches that of the SiN film, thereby increasing the dielectric constant of the SiOCN film.